The use of electrical devices in hazardous areas may lead to an increased risk of a fire or explosion triggered by the presence of the electrical device. For instance, an electrical device may serve as an ignition source in a hazardous area containing flammable fluids or vapors. For this reason, electrical devices used in hazardous areas are often required to be certified according to the requirements specified in that particular jurisdiction. Further, often the types of protections required vary depending on the risks and hazards involved.
The types of hazardous environments are broken down into three classes, with each class focusing on different types of hazardous materials in the surrounding atmosphere. For instance: Class I areas include flammable gasses or vapors present in the air in sufficient quantities to produce an explosion in the presence of an ignition source; Class II areas include the presence of combustible dusts; and Class III areas include ignitable fibers or other materials too heavy to be suspended in the air in sufficient quantities to produce an ignitable mixture (e.g., wood chips, cotton, nylon, etc.). These hazardous area environments are further explained in the ANSI/ISA-12.12.01 standards. Two common types of hazardous areas requiring protection for electrical devices are areas that contain flammable vapors and areas containing dust or other particulates susceptible to ignition. Further, each class is divided into two divisions based on the probability of hazardous materials being present in an ignitable or combustible concentration in the surrounding air. Division 1 defines hazardous environments where the pertinent hazardous material (e.g., vapors, dust, fibers) is present during normal conditions. Division 2 defines hazardous environments where the pertinent hazardous material is present only in abnormal or fault conditions (e.g., in the event of a container failure or other leak).
Regarding Class I hazardous environments involving flammable vapors, an electrical device may be used in such an area via an explosion proof enclosure or assembly configured to keep an internal explosion within the explosion proof assembly from escaping outward, where it would ignite vapors outside of the enclosure. Thus, with regard to environments having flammable vapors, explosion proof assemblies are designed to both prevent the entry of flammable materials into the enclosure and also, in the event of an explosion within the enclosure, to prevent the escape of hot or burning material from escaping the enclosure. Regarding Class II hazardous environments involving ignitable dusts and particulates, an electrical device may be used in such an area via a dust-ignition proof enclosure or assembly that is configured to prevent ignitable materials from entering the enclosure and by containing any arcs, sparks or heat within the enclosure that may ignite dust or other particulates in the surrounding environment. Also, there exists assemblies and enclosures for use with an electrical device that are referred to as “intrinsically safe,” where an intrinsically safe assembly including an electrical device is incapable of releasing sufficient electrical or thermal energy to cause ignition of a specific hazardous substance Class I, Class II and Class III substances) under normal or abnormal conditions. Further, “nonincendive” components are nonsparking and incapable of releasing sufficient electrical/thermal energy to cause ignitions to hazardous substances during normal (i.e., Division 1) operating conditions.
While assemblies or enclosures have been developed for use in hazardous areas, these components are often expensive and not configured for use with particular electrical devices. Also, these components may only satisfy the requirements for a particular class and division, and thus may not be used in other hazardous environments or in hazardous environments under abnormal conditions (i.e., Division 2 conditions). Further, these components may be cumbersome and restrict the functionality of the electrical device being protected. For instance, these components may be permanently coupled to the protected electrical device, restricting the use of multiple electrical devices with the same enclosure. Thus, there is a need in the art for an intrinsically safe or explosion proof assembly and/or enclosure capable of being safely used in varying types of conditions hazardous environments. Also, it would be beneficial if such an enclosure was not permanently coupled to or formed integrally with the protected electrical device, allowing the use of different electrical devices with the same enclosure. Moreover, it would be beneficial if such an enclosure was quickly and conveniently separable from the protected electrical device.